316L, Delta Ferrite & Sigma Phase
316L, Delta Ferrite & Sigma Phase
(OP)
Doing a little investigation and claim upfront to not be an expert but looking for opinions:
MIG welding 10ga 316L SS to 2" sch40 316L SS pipe, .045 316Lmetal core wire. Sheet chemistry below. Assuming there is not excessive delta ferrite present before welding, what is the likelihood that a)additional ferrite is created and b) sigma phase could occur in an estimated time of 5 mins in the zone for sigma phase formation?
I'm sure there details needed that aren't provided, but inquire or please give general statement regarding sigma phase formation.
Thanks.
C .01
SI .28
MN 1.16
P .02
S <.0005
CR 16.62
MO 2.07
NI 10.12
CU .42
AL <.001
B .0013
CO .42
NB .06
SN .006
TI .005
V .11
W .09
FE 68.51
MIG welding 10ga 316L SS to 2" sch40 316L SS pipe, .045 316Lmetal core wire. Sheet chemistry below. Assuming there is not excessive delta ferrite present before welding, what is the likelihood that a)additional ferrite is created and b) sigma phase could occur in an estimated time of 5 mins in the zone for sigma phase formation?
I'm sure there details needed that aren't provided, but inquire or please give general statement regarding sigma phase formation.
Thanks.
C .01
SI .28
MN 1.16
P .02
S <.0005
CR 16.62
MO 2.07
NI 10.12
CU .42
AL <.001
B .0013
CO .42
NB .06
SN .006
TI .005
V .11
W .09
FE 68.51





RE: 316L, Delta Ferrite & Sigma Phase
RE: 316L, Delta Ferrite & Sigma Phase
RE: 316L, Delta Ferrite & Sigma Phase
RE: 316L, Delta Ferrite & Sigma Phase
I could buy fatigue crack propagation, especially if the item was not adequately supported versus sigma phase. Proof would be metallographic examination to confirm if sigma phase developed.
RE: 316L, Delta Ferrite & Sigma Phase
RE: 316L, Delta Ferrite & Sigma Phase
RE: 316L, Delta Ferrite & Sigma Phase
Maui
RE: 316L, Delta Ferrite & Sigma Phase
RE: 316L, Delta Ferrite & Sigma Phase
John Stanley P.E.
RE: 316L, Delta Ferrite & Sigma Phase
Generalpatton, here's more than you probably ever wanted to know about sigma phase:
http://www.hindawi.com/journals/isrn/2012/732471/
Maui
RE: 316L, Delta Ferrite & Sigma Phase
RE: 316L, Delta Ferrite & Sigma Phase
In materials with delta ferrite and the associated non-uniform chemistry sigma will form at the edges (where delta ferrite and grain boundaries intersect) very quickly.
I have done tests with both ferritic stainless grades and duplex.
The samples were under annealed, just enough to get them single phase, but not enough to homogenize the chemistry (they all met spec).
In well annealed samples sigma took hours to form, in the under annealed ones it took less than 10 min.
In some samples it took less than 30 sec.
Prior therm-mechanical history is large factor.
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P.E. Metallurgy, Plymouth Tube
RE: 316L, Delta Ferrite & Sigma Phase